The Studies of the Causes and Effects of Smoking Cessation are being carried out at the Jerry L. Pettis Memorial Veterans Administration (VA) Medical Center in Loma Linda, California. As a supplement to an ongoing VA protocol, ambulatory veterans from the VA Preventive Medicine Clinic and the VA Stop Smoking Classes are being recruited to participate in this two pronged study to test whether immunoglobulin levels change after smoking cessation and to evaluate possible hereditary influences on smoking behaviors. Questionnaires regarding past smoking and success in smoking cessation, as well as blood from each subject are being delivered to our laboratory for molecular analyses. We are evaluating differences in IgG2 levels between subjects that do versus those that do not succeed in quitting smoking. This information is relevant to periodontal disease, since it has been found that smoking tends to decrease IgG2 levels and also increases risk of periodontal disease. We are also planning to study genetic markers of the dopamine pathways that have been suggested by previous studies to influencing addiction including smoking behaviors. The study population will ultimately consist of approximately 300 (male and female) ambulatory veterans who are enrolled in the ongoing Smoking Cessation Program.